SD_BUS_SLOT_SET_USERDATA(3)sd_bus_slot_set_userdataSD_BUS_SLOT_SET_USERDATA(3)

NAME
       sd_bus_slot_set_userdata, sd_bus_slot_get_userdata - Set and query the
       value in the "userdata" field

SYNOPSIS
       #include <systemd/sd-bus.h>

       void* sd_bus_slot_set_userdata(sd_bus_slot* slot, void* userdata);

       void* sd_bus_slot_get_userdata(sd_bus_slot* slot);

DESCRIPTION
       The userdata pointer allows data to be passed between the point where a
       callback is registered, for example when a filter is added using
       sd_bus_add_filter(3) or an asynchronous function call is made using
       sd_bus_call_async(3), and the point where the callback is called,
       without having any global state. The pointer has type void* and is not
       used by the sd-bus functions in any way, except to pass to the callback
       function.

       Usually, the userdata field is set when the slot object is initially
       registered.  sd_bus_slot_set_userdata() may be used to change it later
       for the bus slot object slot. Previous value of the field is returned.
       The argument and returned value may be NULL. It will be passed as the
       userdata argument to the callback function attached to the slot.

       sd_bus_slot_set_userdata() gets the value of the userdata field in the
       bus slot object slot.

RETURN VALUE
       On success, these functions return the value of the userdata field
       before the function call. If the slot object is NULL, NULL will be
       returned to signify an error, but this is not distinguishable from the
       userdata field value being NULL.

NOTES
       These APIs are implemented as a shared library, which can be compiled
       and linked to with the libsystemd pkg-config(1) file.

SEE ALSO
       systemd(1), sd-bus(3), sd_bus_slot_set_destroy_callback(3),
       sd_bus_add_match(3), sd_bus_slot_get_current_userdata(3)

systemd 252                                        SD_BUS_SLOT_SET_USERDATA(3)

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